Adult female rhesus monkeys will be fed diets containing 5, 25, and 50 ppt of 2,3,7,8-tetrachlorodibenzo-p-dioxin for a period of at least 2 years. During this period, the animals will be evaluated for changes in general body health. In addition, the animals will be bred after 6 months of exposure to these diets and the effects of the TCDD on conception, and frequency of abortions will be determined. We will also be evaluating the effects of TCDD on fetal and neonatal development. Surviving infants will be tested for modifications in their learning and behavioral development.